The present invention relates to apparatus and method for controlling a stability of a vehicular attitude using a vehicular braking system, particularly, the apparatus and method described above in which a braking force is controlled according to a variation in the vehicular attitude so as to stabilize the vehicular attitude.
A Japanese Patent Application First (unexamined) Publication No. Heisei 6-247269 published on Sep. 6, 1994 exemplifies a previously proposed vehicular attitude control apparatus.
In the above-identified Japanese Patent Application Publication, a vehicular attitude angle (.beta.) is determined according to a yaw rate and a vehicular steering angle and, where the vehicular attitude angle (.beta.) exceeds a limit value, a vehicular attitude purpose controller determines that it is a time to start the control and varies a wheel cylinder pressure in a vehicular braking system through a hydraulic pressure development equipment so that the attitude angle (.beta.) is increased or such a situation that it is impossible for the attitude angle to be developed during a vehicular turning is avoided.
It is a general practice in a vehicle that vehicular braking pressure distribution conduits are of two mutually crossing types by which wheel cylinders arranged around from left and right road wheels are mutually connected and by which wheel cylinders arranged around front right road wheel and rear left road wheel are mutually connected and the two mutually crossing vehicular braking pressure distribution circuits are connected to a master cylinder (which serves to develop a braking operation responded liquid pressure).
If the above-described vehicular attitude control apparatus described in the above-identified Japanese Patent Application First Publication is applied to the braking system in which the two separate braking pressure distribution conduits are disposed, suppose that a liquid pressure from a control purpose liquid pressure source such as a pump is supplied to the wheel cylinders arranged around the front left and right road wheels or arranged around the same sided front and rear road wheels.
In this case, since the two braking pressure distribution conduits are interrupted from the master cylinder, suppose also that a vehicular driver operates a braking element to demand the braking during an execution of the vehicular attitude control.
In this case, since the two separate braking pressure distribution conduits are interrupted from the master cylinder, the liquid pressure developed in response to the braking demand by the driver is not supplied to the corresponding wheel cylinders. Consequently, the braking operated liquid pressure according to the driver's intention cannot be developed in the braking system.
To solve this problem, a force applied to the braking element to demand the braking or the liquid pressure in the master cylinder may be detected and the liquid pressure corresponding to the detected force or liquid pressure may be considered to be supplied to the corresponding wheel cylinders from the control purpose liquid pressure source. However, the above-described countermeasure introduces a complication of control and an expensive detector for detecting the force or liquid pressure in the master cylinder is needed. In addition, the complicated control and the complicated structure in the vehicular attitude control apparatus may be resulted in a reduction of reliability.